Removing flavor changing neutral interactions from leptoquark exchange

Abstract

We look for a mechanism that removes without numerical fine tuning the strong constraint imposed by the flavor changing neutral current interaction of leptoquark exchange. If n x n degenerate leptoquarks couple universally to n generations of quarks and leptons in the weak basis, not only can the neutral current interactions be flavor diagonal, but also the charge current interaction takes exactly the same form as W exchange at low energies. Atomic parity violation still imposes tight constraints. Electroweak doublets with some left-right symmetry have the best chance to be the lightest leptoquarks.